Differential and collaborative actions of Rad51 paralog proteins in cellular response to DNA damage

Metazoan Rad51 plays a central role in homologous DNA recombination, and its activity is controlled by a number of Rad51 cofactors. These include five Rad51 paralogs, Rad51B, Rad51C, Rad51D, XRCC2 and XRCC3. We previously hypothesized that all five paralogs participate collaboratively in repair. However, this idea was challenged by the biochemical identification of two independent complexes composed of either Rad51B/C/D/XRCC2 or Rad51C/XRCC3. To investigate if this biochemical finding is matched by genetic interactions, we made double mutants in either the same complex (rad51b/rad51d) or in both complexes (xrcc3/rad51d). In agreement with the biochemical findings the double deletion involving both complexes had an additive effect on the sensitivity to camptothecin and cisplatin. The double deletion of genes in the same complex, on the other hand, did not further increase the sensitivity to these agents. Conversely, all mutants tested displayed comparatively mild sensitivity to γ-irradiation and attenuated γ-irradiation-induced Rad51 foci formation. Thus, in accord with our previous conclusion, all paralogs appear to collaboratively facilitate Rad51 action. In conclusion, our detailed genetic study reveals a complex interplay between the five Rad51 paralogs and suggests that some of the Rad51 paralogs can separately operate in later step of homologous recombination

Promoting effect of basic fibroblast growth factor in synovial mesenchymal stem cell-based cartilage regeneration

Synovial mesenchymal stem cell (SMSC) is the promising cell source of cartilage regeneration but has several issues to overcome such as limited cell proliferation and heterogeneity of cartilage regeneration ability. Previous reports demonstrated that basic fibroblast growth factor (bFGF) can promote proliferation and cartilage differentiation potential of MSCs in vitro, although no reports show its beneficial effect in vivo. The purpose of this study is to investigate the promoting effect of bFGF on cartilage regeneration using human SMSC in vivo. SMSCs were cultured with or without bFGF in a growth medium, and 2 × 105 cells were aggregated to form a synovial pellet. Synovial pellets were implanted into osteochondral defects induced in the femoral trochlea of severe combined immunodeficient mice, and histological evaluation was performed after eight weeks. The presence of implanted SMSCs was confirmed by the observation of human vimentin immunostaining-positive cells. Interestingly, broad lacunae structures and cartilage substrate stained by Safranin-O were observed only in the bFGF (+) group. The bFGF (+) group had significantly higher O’Driscoll scores in the cartilage repair than the bFGF (−) group. The addition of bFGF to SMSC growth culture may be a useful treatment option to promote cartilage regeneration in vivo.Okamura G., Ebina K., Hirao M., et al. Promoting effect of basic fibroblast growth factor in synovial mesenchymal stem cell-based cartilage regeneration. International Journal of Molecular Sciences, 22, 1, 1. https://doi.org/10.3390/ijms22010300

Knee hemarthrosis after arthroscopic surgery in an athlete with low factor XIII activity

Abstract We report a thirteen-year-old tennis player with knee hemarthrosis caused by low factor XIII activity. She visited our hospital because of medial peripatellar pain for two years. Although there was no abnormal sign in X-ray or MRI, diagnostic arthroscopy was performed. It revealed some cartilage debris, medial plica and complete septum of suprapatellar plica. Removing the debris by washing out and resecting the medial plica, she could return to play tennis without perioperative symptom. Two months after the first operation, her knee got swelling without any apparent cause. Since 20 ml blood was aspirated twice and MRI revealed suprapatellar mass, we performed arthroscopy again. Suprapatellar mass was old blood clot covered with complete suprapatellar plica. Resection of suprapatellar plica and washing out blood clot were performed, and severe postoperative hemarthrosis was progressively occurred. As factor XIII level was 54% preoperatively, we diagnosed that this condition was caused by low activity level of the factor and administered factor XIII concentrates. The level got improved to 129% and then hemarthrosis gradually relieved. She had no signs of recurrence. We should keep in mind of low factor XIII activity case in case of unexplained postoperative hemarthrosis after arthroscopy because consumption of the factor might promote this condition.</p

Early reconstruction should be considered in younger patients with symptomatic mucoid degeneration of the anterior cruciate ligament

Background: Mucoid degeneration of the anterior cruciate ligament (ACL) is mostly observed in middle-aged patients with knee pain and limited range of motion. Although arthroscopic resection of the degenerated ACL is the treatment of choice following the failure of conservative management, the extent of the excision and subsequent ACL reconstruction for postoperative knee instability remains controversial. Case reports: We present four cases of mucoid degeneration of the ACL in patients aged <40 years, and suggest a suitable treatment strategy for younger patients. All four patients (mean age, 33.8 years) were diagnosed with mucoid degeneration of the ACL based on characteristic clinical symptoms and magnetic resonance imaging. Arthroscopic resection of the affected portion of the ACL was performed as follows: partial resection in two cases with limited hypertrophy, and total ACL resection in the remaining two cases with degeneration involving the entire ligament. Preoperative symptoms disappeared in all cases after resection of the lesions. In the two patients with partial resection, the ACL was completely torn during subsequent sports activities despite showing no symptoms of instability for 2 years postoperatively. All four patients, including the two treated by total resection, underwent ACL reconstruction using an autogenous hamstring tendon. Conclusion: Considering the rupture of residual ACL fibres after partial resection and the inevitability of total ACL resection due to degeneration of the entire ligament, ACL reconstruction should be considered in younger patients with symptomatic mucoid degeneration of the ACL

Simultaneous MPFL and LPFL reconstruction for recurrent lateral patellar dislocation with medial patellofemoral instability

We report an extremely rare case of both recurrent lateral patella dislocation and medial patellofemoral instability, following prior operations to correct patella maltracking. Manual translation of the patella revealed medial and lateral instability with a positive apprehension sign. 3-D computer modelling of kinematics based on MRI data demonstrated that the patella deviated laterally at full extension and translated medially with knee flexion. The medial and lateral patellofemoral ligaments were reconstructed simultaneously with hamstring tendons, alleviating peripatellar pain and patellar instability in both directions

Promoting Effect of Basic Fibroblast Growth Factor in Synovial Mesenchymal Stem Cell-Based Cartilage Regeneration

Synovial mesenchymal stem cell (SMSC) is the promising cell source of cartilage regeneration but has several issues to overcome such as limited cell proliferation and heterogeneity of cartilage regeneration ability. Previous reports demonstrated that basic fibroblast growth factor (bFGF) can promote proliferation and cartilage differentiation potential of MSCs in vitro, although no reports show its beneficial effect in vivo. The purpose of this study is to investigate the promoting effect of bFGF on cartilage regeneration using human SMSC in vivo. SMSCs were cultured with or without bFGF in a growth medium, and 2 &times; 105 cells were aggregated to form a synovial pellet. Synovial pellets were implanted into osteochondral defects induced in the femoral trochlea of severe combined immunodeficient mice, and histological evaluation was performed after eight weeks. The presence of implanted SMSCs was confirmed by the observation of human vimentin immunostaining-positive cells. Interestingly, broad lacunae structures and cartilage substrate stained by Safranin-O were observed only in the bFGF (+) group. The bFGF (+) group had significantly higher O&rsquo;Driscoll scores in the cartilage repair than the bFGF (&minus;) group. The addition of bFGF to SMSC growth culture may be a useful treatment option to promote cartilage regeneration in vivo

Vibration acceleration promotes bone formation in rodent models

<div><p>All living tissues and cells on Earth are subject to gravitational acceleration, but no reports have verified whether acceleration mode influences bone formation and healing. Therefore, this study was to compare the effects of two acceleration modes, vibration and constant (centrifugal) accelerations, on bone formation and healing in the trunk using BMP 2-induced ectopic bone formation (EBF) mouse model and a rib fracture healing (RFH) rat model. Additionally, we tried to verify the difference in mechanism of effect on bone formation by accelerations between these two models. Three groups (low- and high-magnitude vibration and control-VA groups) were evaluated in the vibration acceleration study, and two groups (centrifuge acceleration and control-CA groups) were used in the constant acceleration study. In each model, the intervention was applied for ten minutes per day from three days after surgery for eleven days (EBF model) or nine days (RFH model). All animals were sacrificed the day after the intervention ended. In the EBF model, ectopic bone was evaluated by macroscopic and histological observations, wet weight, radiography and microfocus computed tomography (micro-CT). In the RFH model, whole fracture-repaired ribs were excised with removal of soft tissue, and evaluated radiologically and histologically. Ectopic bones in the low-magnitude group (EBF model) had significantly greater wet weight and were significantly larger (macroscopically and radiographically) than those in the other two groups, whereas the size and wet weight of ectopic bones in the centrifuge acceleration group showed no significant difference compared those in control-CA group. All ectopic bones showed calcified trabeculae and maturated bone marrow. Micro-CT showed that bone volume (BV) in the low-magnitude group of EBF model was significantly higher than those in the other two groups (3.1±1.2mm³ v.s. 1.8±1.2mm³ in high-magnitude group and 1.3±0.9mm³ in control-VA group), but BV in the centrifuge acceleration group had no significant difference compared those in control-CA group. Union rate and BV in the low-magnitude group of RFH model were also significantly higher than those in the other groups (Union rate: 60% v.s. 0% in the high-magnitude group and 10% in the control-VA group, BV: 0.69±0.30mm³ v.s. 0.15±0.09mm³ in high-magnitude group and 0.22±0.17mm³ in control-VA group). BV/TV in the low-magnitude group of RFH model was significantly higher than that in control-VA group (59.4±14.9% v.s. 35.8±13.5%). On the other hand, radiographic union rate (10% in centrifuge acceleration group v.s. 20% in control-CA group) and micro-CT parameters in RFH model were not significantly different between two groups in the constant acceleration studies. Radiographic images of non-union rib fractures showed cartilage at the fracture site and poor new bone formation, whereas union samples showed only new bone. In conclusion, low-magnitude vibration acceleration promoted bone formation at the trunk in both BMP-induced ectopic bone formation and rib fracture healing models. However, the micro-CT parameters were not similar between two models, which suggested that there might be difference in the mechanism of effect by vibration between two models.</p></div

Micro-CT analysis of rib fracture sites among vibration acceleration groups and constant acceleration groups.

<p>Micro-CT analysis of rib fracture sites among vibration acceleration groups and constant acceleration groups.</p